1. Field of the Invention
The present invention relates to an airbag device for front passenger's seat to be mounted on an instrument panel in front of front passenger's seat.
2. Description of Related Art
In the prior art, Japanese Patent Laid-Open No.2002-255004 discloses an airbag device for front passenger's seat including an airbag folded and housed in a case. When fed with inflation gas, the airbag pushes and opens a door portion in an airbag cover arranged on top face of instrument panel, and protrudes upward and deploys rearward of vehicle.
As a shape as completely deployed, the airbag of this airbag device includes a passenger's side wall arranged generally vertically to confront a passenger, and a circumferential wall extending from outer edge of the passenger's side wall and narrowing generally conically as it goes forward. Moreover, the airbag is provided in lower front part of the circumferential wall at complete inflation with a gas inlet port arranged generally horizontally, and is attached to the case at periphery of the gas inlet port.
Before being housed in the case, the airbag is folded through preparatory folding step and regular folding step, the regular folding step further consisting of transverse folding step to fold the airbag on transverse folds and reduce a dimension in front-rear direction, and vertical folding step to fold the airbag on folds along front-rear direction to reduce a transverse width.
In a preparatorily folded state, a portion near an upper edge of the passenger's side wall is located to confront the gas inlet port, and the passenger's side wall is flatly developed so as to overlap with a lower part of the circumferential wall.
In this airbag device for front passenger's seat, the airbag admits inflation gas from the gas inlet port and deploys while unfolding the transverse and vertical folds. At this time, since the portion near the upper edge of the passenger's side wall is disposed in a position to confront the gas inlet port in the preparatory folding step, the portion is pushed up intensely by a pressure of inflation gas having just flown-in prior to other portions of the passenger's side wall such as lower part. Consequently, the passenger's side wall is easily disposed generally vertically.
Moreover, quick lifting up of the portion near the upper edge of the passenger's side wall contributes to quick unfolding of the transverse and vertical folds, and further contributes to quick deployment of the passenger's side wall.
Therefore, upon airbag deployment, the airbag device for front passenger's seat in the prior art arranges the passenger's side wall, which is generally perpendicular to a gas inlet port vicinity, in a generally vertical condition, and develops the airbag in a fully open state so as not to apply partial pressure to a passenger.
However, the airbag device for front passenger's seat in the prior art still has a room for improvement in moving an upper part of rear face of the airbag further quicker than a lower part.
That is, if the upper part of the rear face of the airbag moves rearward quicker than the lower part during airbag deployment, an entire rear face of the deploying airbag further easily takes a vertical position in moving rearward. Even if the deploying airbag engages an advancing passenger, the airbag protects the passenger properly without applying partial pressure to the passenger.